Publication Date

Spring 2023

Degree Type


Degree Name

Master of Science (MS)


Chemical and Materials Engineering


Sang-Joon Lee

Subject Areas

Chemical engineering


Altered gravitational conditions result in changes in biological function. Studies in microgravity have shown irregularities in fluid redistribution within the vascular system. In order to study these irregularities, a cell culture perfusion system is necessary. Bubbles can proliferate in closed-loop systems and are detrimental to cells. However, the effects of bubbles in a closed-loop system in microgravity are unknown. Accordingly, the hypothesis of this investigation is that the absence of a constant-direction gravitational body force will exacerbate the presence of bubbles in a closed-loop microfluidic perfusion system. In order to examine the hypothesis, a closed-loop microfluidic cell culture perfusion system that can prescribe shear stresses and simulate different gravity conditions was developed. Microgravity was simulated by mounting and running the perfusion system on a random positioning machine. Data from discontinuities in liquid-phase flow were compared at low and high shear stresses in normal gravity and microgravity. At microgravity, the number of liquid-phase discontinuities increased by more than three orders of magnitude at similar shear stresses. These findings support the hypothesis that microgravity conditions can exacerbate bubbles. This presents a unique challenge for mitigating bubbles in long-duration, unattended experiments.

Available for download on Monday, August 31, 2026